A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
The Oracle of the Void entry on Kyuden Kitsune mentions an erratum that there's no longer a restriction on playing Mantis clan personalities off that box... however, in viewtopic.php?f=59&t=75249&p=985946 it was ruled that "if the Personality has the base "Mantis Clan" keyword, he will not join you and his entering play under your control will fail"
So which is correct? Hopefully NOT the Oracle...
The Oracle of the Void entry on Kyuden Kitsune mentions an erratum that there's no longer a restriction on playing Mantis clan personalities off that box... however, in viewtopic.php?f=59&t=75249&p=985946 it was ruled that "if the Personality has the base "Mantis Clan" keyword, he will not join you and his entering play under your control will fail"
So which is correct? Hopefully NOT the Oracle...
The Oracle is the more-current source and correct.
The ruling you quoted was from 2009, before the Oracle existed.
When compiling the Oracle, with the switch from "Yoritomo's Alliance" being the identifying keyword of the Clan to "Mantis Clan" in Gold (rather than the pre-Gold situation of the latter implying the former), it was decided to simply remove the trait due to its incongruity with current paradigms.